Spark plug



May 24, 1938. E. F. KOEHLER ET AL SPARK :PLUGV Filed -April 9, 193e gv f Patented May 24, 1938 liA'rl-:NTv OFFICE 2.11:;,251 smal; PLUG Emma Koehler, Berlin, and Gustave w.

Goerner,Bourne, Mass.

Application April 931936, Sel'lill No. 73,452

6 Claims. (Cl. 123-169) i Our invention relates to spark plugs for internal combustion engines and has for its principalobject to provide an improved negative or ground electrode and means for mounting the same, so that this electrode may bevreadily replaced and renewed when partly burned away or distorted by use. A further object has been to provide a ground electrode which shall cause the spark to be spread and distended so that it may l0 perform its function more emciently.

Our device may be best understood by reference to the accompanying drawing in which:

Fig. 1 is an elevation of our improved spark plug. l

Fig. v2 is a vertical section through the 'plug of Fig. 1..

Fig. 3 shows a ilrst modified form of our invention in which the removable'ground electrode instead of being curved in an arc below the end of the positive electrode, asin Fig.'1, is curved in an arc laterally disposed with respect to the end of the positive electrode; the lower part of the shell and insulator core being shown in vertical, medial cross section. Fig. 4 is an enlarged section of the lower portion of the shell showing the grooves wherever a ground electrode may be removably mounted.

Fig. 5 shows in section the shell of Fig. 4 with Athe ground electrode of Figs. 1 and 2 mounted therein and the insulator core and positive electrode in place. .v

Fig. 6` is an enlarged cross-section on line 6-6 of Fig. 3, with the insulator core removed.

Fig. 'I is a cross-section on line 'l--1 of Fig. 5 with the insulator core removed.

Fig. 8 is an enlarged section on line l-l of Fig.

3 with the insulator core removed.

Fig. 9 shows in cross-section corresponding to that of Fig. 6 a secondmodifled form of our ino vention wherein appear two removable ground electrodes each organized and removably mounted like the other on its `respective side of the end of the positive electrode.

Fig. 10 is an enlarged bottom viewof the spark plug shown in Fig. 1.

Fig. 11 is a.v perspective view of a removable ground electrode suchv as is shown in Figs. 1`

and 2.

Fig. 12 is a cross section corresponding to Fig. u 6 showings third modiiled form inv which a pair of parallel removable ground electrodesl are ernployed.y

Referring now to the'. drawingfin which like reference numerals indicate like parts, `l yis a shell provided with an extension 2 of reducedy diameter and threaded to enter the usual threaded hole in the casing ofthe motor. The bore! of the casing VI tapers slightly in a portion of its extent, as mostI clearly shown in Fig. 4, thereby providing a seat for a correspondingly tapered 5 portion of the porcelain insulator 4. The upper part of the insulator 4 is of uniform, reduced diameter aiording an annular shoulder 5 against which is seated the threaded extension of the jam nut 6 which is screwed 4into the threaded top of l0 the bore 3 of the casing I,- thereby pressing the tapered portion of the insulator 4 into iirm engagement with the tapered portion of the bore 3 of the casing I.

The insulator 4 is provided with a central bore 'l5 in which is inserted the positive electrode 1 the top of which is press-tted into hole I in the base of the metal insulator cap 9 the cylindrical portion I0 of which is screw threaded to engage screw threads in the top cavity of the insulator 4. .o

A binding post II, integral with the cap 9 is screw threaded to receive the conventional knurled binding nut I2 for attaching thev high tension wire.

The interior of the threadedextension 2 of the 25 casing is provided with opposite grooves I3 which enter an annular groove I4 located immediately below the narrowest part `of the tapered bore 2 of the casing I. Within these grooves I3 and I4 is removably mounted the steel wire ground elec- 30- trode I5 which may be inserted in place when 'the insulator 4 has been removed and will be locked in place by the insulator when the insulator is returned to position as shown in Fig. 5.

As will be more readily understood frqm an ex- 3:, amination of Fig. 11 theelectrode I5 is generally re-sliaped andprovided with straight upwardly extending parts or legs which are slightly spread apart so that the free ends of the legs which take the form of curved lateral arms I8 mayafter 4o the tops of the straight upwardly extending are slightlypressed together to permit insertion within the' extension 2, be forced withviirrn'spring' tension into engagement with the ground part I4 of the casing I when the straight upwardly ex- 45 tending parts of the electrode I5 are entered in grooves l'and rmly seated there. ,f. 2 The lower central part I1 of the ground electrode I5 is preferably given a substantially reg-v ular arc of curvature centered on the middle of 5o I the tip of the positiveelectrode l; and, asshown invFigs. 1 2. 5,'7, 10 andy 11, this arc of curvature may be vertically disposed beneath the tip of the electrode 1, or, as shown in Figs. 3, 6 and 8 this arc I1 may bev laterally disposed with respect to that shown in Fig. 9, a pair of oppositely placed 'ground electrodes each formed with a laterally disposed arc I1' may be employed, the ares being oppositelypositioned so as substantially to surround the end of the Y,positive electrode 1. In

this form oi construction lthe vertical grooves Il'.

corresponding to the grooves Il of Fig. 6 are made wider to accommodate the pair oi' ground electrodes and the curved arms il' extend toward each -other instead of extending in opposite direc- 1.-, consumidas.

A further modiiied form appears in Fig. 12 a pair oi' ground electrodes it* each`organized in the general manner heretofore described except that the vertical slots I32 wherein each is mount- I' 20 ed are not diametrioallyopposite each other but so arranged that the two ground electrodes i5 bridge straight across the base ofthe casing l parallel to each other'and upon oppomte sides of the positive electrode I so as to form doublespark gaps, and the arms I6 of each of these ground electrodes, like those'shownl in Fig. 6 previously described, extend toward each other.l

From the foregoing description it will be readily understood that our removably mounted ground electrodes may be quickly and easily replaced when they becomeburned out or distorted by use, and that while in place they will maintain at all times an extensive, firm, spring pressed contact withA the shell or casing o l' the plug so as' 3 5 to aiiord a good electrical connection.

I'he arc I1 or i1' oi' the ground electrodes being substantially'a part of a true circle centered onthe axis of the positive electrode will result in a broad, fan shaped spark giving excellent ignition;

a and where the parallel arrangement of cross members oi' Fig. 12 is employed the cross members may be, if necessary, slightly pinched together and permanently distorted to compensate for the burning away o f adjacent areas ofthe podtive 5 and ground electrodes which has too much widened the spark gaps. y Having thus fully described our invention what we claim is:

l. In a spark plug the combination of a casing 5o. provided with a bore which is ,cylindrical at its form arcuate portions adapted to lower end and provided with an annular groove, a ground electrode the ends of which arebent toengage said groove and the central portion oi 55 which is arranged to underlie and bridge across said bore and form a spark gap between said central portion and a positive electrode, a positive electrode and an insulator for said positive electrode adapted. to nt within said bore Rnd t0 retain .o the ends of saidground electrodewithin said 8l00ve.

2. In a spark plug provided with a bore which is cylindrical at its ilt within and thecombination of a casing lowerr end and provided with an annular `groove and with oppositely placed straight grooves communicating with said annular groove. a generally U-shape ground electrode the legs loi' which ilt ed to ilt within said bore and to retain the ends f' of said ground electrode within said annulargroove. 3. A spark plug according to claim 1 in which the central portion of the bridge between the legs of the ground electrode is bent to 'forman arc of a circle which is centered with respect to the end of the positive electrode, the arcuate central -portion beingconnected to the legs by generally radially disposed bridge portions.

4.v In a spark plug the combination 'of a casing provided with a bore which is cylindrical at its lower end, a positive electrode centrally mounted in said bore, an insulator for said positive electrode, a pair of negative electrodes mounted in said casing in a manner whereby they may bridge across said bore, said electrodes lying upon opposite sides of the extremity of said positivev electrode in a parallel manner, said insulator maintaining said'negative electrodes in proper operative spaced 'relation to the positive electrode.

5. In a spark plug the combination of a casing provided with a bore which is cylindrical at its -lower'end, a positive 'electrode centrally mounted an insulator for said positive elec-Y in said bore, trode, there being an annular groove in the casing opening into the'cylindrical bore, a pair oi generally U-shape negative electrodes mounted in .said casing, thefree ends of the legs of each U- ,shape electrode being bent towards one another to form arcuate portions which t withinY the groove, said negative electrodes having portions which bridge the legs thereof to lie upon opposite sides of ,theyextremity oi' said positive electrode in oppositely extending similar arcs centered about the end of said positive electrode.

6. In\a sparkplug the combination of a cas-l ing having a bore which is cylindrical atits lower end and provided with a cavity opening into the ERNEST F. Komm GUsrsvE W. comm. 

